The production of oil and/or gas in subterranean wells frequently encounters extreme erosion, experienced when oil or gas escapes from the formation at a high velocity, carrying with it entrained abrasive solids such as silt, sand, clay and clay sized debris. The resultant blast can quickly cut through metal surfaces such as the well tubing, and erosion resistant blast joints have been developed for this application.
In prior U.S. Pat. Nos. 4,028,796 and 4,141,386 there is disclosed a blast joint which is formed with a plurality of cemented tungstun carbide rings stacked in an end face to face array on a string of production tubing. The rings have lap finished end surfaces and are compressed in the assembly by resilient spring washers with the entire assembly retained by collars distally carried on the length of tubing. The collars are slidably received over the tubing and are secured in place by a plurality of set screws which, when tightened, project into binding engagement with the production tubing. This construction has successfully prevented erosion of the production tubing, however, it is not well suited for applications in extremely corrosive environments such as when hydrogen sulfide, carbon dioxide, etc. are encountered. When such corrosive products are encountered, corrosion can occur and this corrosion is concentrated at stress points such as the points of engagement of the set screws with the production tubing or the set screws themselves, releasing the assembly.